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This crustose bark epiphyte has a rather scruffy, scurfy, grey, cracked thallus dissolving into a crust of granules (soredia). Many of these arise from within the thallus and can be told by their blue-grey to pale-green-grey speckling. The thallus which turns yellow with K (Potassium hydroxide) is also Pd + red. It is a pollution-tolerant species that has adapted to wayside habitats, for example, large car parks. It grows on the flat surfaces between the bark crevices of rough-barked trees — ash, birch and alder. Northern half of Ireland, mostly.

Key characteristics

K + yellow, Pd + red thallus. Buellia griseovirens and Mycoblastus caesius are close, but the first has neatly distributed soralia and the second is never with hints of apple-green. Also both are never Pd + red.